Atherosclerotic vascular disease is the leading cause of death in this country. Current therapeutic modalities, however, are not ideal and are associated with significant morbidity, mortality, and expense. The aim of this project is to develop and apply the techniques of angioscopy, hematoporphyrin-laser induced photoatherolysis and laser angioplasty for the treatment of atherosclerotic disease. Specific goals are (A) To develop a fiberoptic waveguide that permits transmission of ultraviolet light and simultaneous visualization and lasing. (B) To evaluate the efficacy of perfulorocarbon solutions and coronary sinus retroprofusion for myocardial oxygenation during temporary obstruction of blood flow. (C) To demonstrate selective hematoporphyrin concentration in atheroma and investigate the possibility of laser activated, hematoporphyrin induced photoatherolysis. (D) To define the dose-response of a variety of lasers on vascular tissue. (E) To examine the physical and chemical changes that occur when vascular tissue is irradiated by laser energy. (F) To determine if photochemical rather than photothermal ablation can be accomplished in vascular tissue. (G) To determine the informational valve of direct intravascular visualization of atherosclerotic disease. (H) To gain initial experience with angioscopy and laser angioplasty in man and to determine the efficacy and safety of these procedures.